Multi-functional polymers

ABSTRACT

A multi-functional polymer defined by the formula
 
(Q—R   n Z—P 2 —Y
 
where (Q—R) n  is a functionality cluster, Q is a functional group, R is a multi-valent organic group, P 2  is a long-chain polymer, n is an integer from about 2 to about 10, Y is a proton, a weak functional group, or a selective functional group, and Z is a branch point where the functionality clusters join the long-chain polymer.

This application gains benefit from U.S. Provisional Patent ApplicationNo. 60/400,340, filed on Aug. 1, 2002.

FIELD OF THE INVENTION

This invention relates to multi-functional polymers and processes formaking the same.

BACKGROUND OF THE INVENTION

In the art of making tires, it is desirable to employ rubbervulcanizates that demonstrate reduced hysteresis loss, i.e., less lossof mechanical energy to heat. Hysteresis loss is often attributed topolymer free ends within the cross-linked rubber network, as well as thedisassociation of filler agglomerates.

Functionalized polymers have been employed to reduce hysteresis loss.The functional group of the functionalized polymer is believed tointeract with a filler particle and thereby reduces the number ofpolymer free ends. Also, the interaction between the functional groupand the filler particles reduces filler agglomeration, which therebyreduces hysteretic losses attributable to the disassociation of filleragglomerates.

One particularly useful functional group is tributyltin. Rubberypolymers containing a tributyltin functionality have produced rubbervulcanizates that demonstrate reduced hysteresis loss. These rubberypolymers have been prepared by anionic polymerization techniques wherebytin-lithio initiators, e.g., tributyltin lithium, have been employed asinitiators.

Further reduction in hysteresis loss has been observed where the rubberpolymers employed in the manufacture of tires contain functionalities atboth the head and tail of the polymer. For example, polybutadiene andpoly(styrene-co-butadiene) have been prepared by initiating theirpolymerization with a tin-lithio initiator, e.g., tributyltin lithium,and terminating the polymerization with alkyltin chlorides, which imparta tin functionality at the end of the polymer chain.

While polymers that have functionalities at both their head and tailhave demonstrated the ability to provide filler-reinforced vulcanizateswith advantageous hysteresis properties, the ability to process thesepolymers is reduced as compared to non-functional polymers. Namely, theability to adequately mix filler particles into the rubber compound hasproven to be problematic because it requires greater mixing energy andmixing time.

Because polymers that provide filler-reinforced vulcanizates withreduced hysteresis loss are important in the manufacture of tires, thereis a need to overcome problems associated with prior art polymers.

SUMMARY

In general the present invention provides a method for decreasinghysteresis loss of rubber vulcanizates without deleteriously impactingthe processability of the rubber composition that yields thevulcanizate, the method comprising employing a multi-functional rubberypolymer in the rubber composition, where the multi-functional polymerincludes at least two functional groups at one end of the polymer chainand the opposite end of the polymer is devoid of a functional group orincludes a weak functional group or functional group that is selectivelyfunctional.

The present invention also includes a process for preparing amulti-functional polymer comprising the steps of preparing amulti-functional macroinitiator by reacting a short-chain living polymerwith a molar deficiency of a macroinitiator linking agent defined by theformulaC═C—R′—C*—Xwhere X is a leaving group, C* is a carbon atom susceptible tonucleophilic attack, and R′ is an organic group that will impact thedouble bond in a manner that will allow the double bond to beanionically polymerized, and polymerizing monomer with themulti-functional macroinitiator.

The present invention further provides a process for preparing amulti-functional polymer comprising the steps of preparing amulti-functional macroterminator by reacting a short-chainfunctionalized living polymer with a macroterminator linking agentdefined by the formula L_(a)SiRA, where Si is a silicon atom, R is anorganic group, L is a leaving group, A is a leaving group that is lessreactive than L, and a is 2 or more, and terminating a living polymerwith the multi-functional macroterminator.

The present invention also includes a process for preparing amulti-functional polymer comprising the steps of polymerizing a heteroblock at the head or tail of a rubbery polymer, where the hetero blockis prepared by polymerizing functional macromonomer, where thefunctional macromonomer is a macromolecule that includes a double bondcapable of being anionically polymerized, a functional group, and anorganic group between the double bond and the functional group where thedistance between the double bond and the functional group is less thanone entanglement length.

The multi-functional polymers of this invention advantageously achievegreater rubber-filler interaction than unfunctionalized polymers, and inmany instances greater than functionalized polymers containing only onefunctional group, and yet they advantageously demonstrate betterprocessability than polymers that are functionalized at the head andtail. Indeed, it has been surprisingly discovered that increasing thenumber of functional groups at or near one end of a polymer chain willincrease the number of polymer chains that are bound to filler particleswithout proportionately decreasing processability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the chemical mechanism by which the formation of themulti-functional initiator is likely to occur.

FIG. 2. is a graphical plot of tan δ as a function of bound rubber forexemplary polymers of this invention and comparative examples.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The multi-functional polymers of this invention include two or morefunctionalities or functional groups at or near one end of the polymerchain. The functional groups advantageously include those groups thatinteract with filler or rubber employed in rubber compounds. In view ofthe discoveries made in this invention, those skilled in the art will beable to synthesize a number of polymer architectures that will provide arubbery polymer having two or more functionalities at or near one end ofa polymer chain.

In one embodiment, the multi-functional polymers include a functionalitycluster and at least one polymer chain attached thereto. Themulti-functional polymers can be represented by the formula

where (Q—R)_(n) is a functionality cluster, Q is a functional group, Ris a multi-valent organic group, P² is a long-chain polymer, n is aninteger from about 2 to about 10, Y is a proton, a weak functionalgroup, or a selective functional group, and Z is a branch point wherethe functionality clusters join the long-chain polymer.

Multi-valent organic groups may include hydrocarbylene groups, which maycontain hetero atoms. Hydrocarbylene groups include alkylene,substituted alkylene, cycloalkylene, substituted cycloalkylene,alkenylene, substituted alkenylene, cycloalkenylene, substitutedcycloalkenylene, arylene, and substituted arylene groups, with eachgroup preferably containing from 1 carbon atom, or the appropriateminimum number of carbon atoms to form the group, up to about 20 carbonatoms. These hydrocarbylene groups may contain heteroatoms such as, butnot limited to, nitrogen, oxygen, silicon, sulfur, and phosphorus atoms.

The polymer P² is preferably a long-chain polymer that include a polymerthat is capable of being synthesized by anionic polymerizationtechniques. Preferably, P² is longer than 1.5, more preferably longerthan 5, even more preferably longer than 20, still more preferablylonger than 50, and even more preferably longer than 100 times theentanglement length of the polymer.

The organic group (R) is preferably a hydrocarbylene group and morepreferably a divalent polymer. Where the multi-valent organic groupincludes a polymer chain, the polymeric chain may include any polymerthat is capable of being synthesized by anionic polymerizationtechniques.

Where the organic group (R) is a divalent polymer, the length of thedivalent polymer chain is preferably less than 1.5 of the entanglementlength, more preferably less than 1.2 of the entanglement length, evenmore preferably less than 1 entanglement length, still more preferablyless than 0.7 of the entanglement length, and even more preferably lessthan 0.5 of the entanglement length. This will result in a functionalitycluster (Q—R)_(n) that includes at least two functionalities orfunctional groups (Q) within three, and preferably two, entanglementlengths. Preferably, the functionality cluster includes at least three,more preferably at least four, and more preferably at least fivefunctional groups within three entanglement lengths. It is alsoadvantageous that the functional groups (Q) within the functionalitycluster (Q—R)_(n) are spaced apart at a minimum distance from oneanother. This minimum distance can be defined with reference to theminimum length of each organic group R. Preferably, the length of R isgreater than 0.05 of the entanglement length, more preferably greaterthan 0.1 of the entanglement length, still more preferably greater than0.2 of the entanglement length, and even more preferably greater than0.3 of the entanglement length.

The entanglement molecular weight is related to the length of thepolymer chain and refers to a number of polymer chain repeating (or mer)units that correspond to a molecular weight sufficiently large forentanglements to occur between molecules of undiluted polymer. Thislength corresponds to a molecular weight where the slope of a plot oflog viscosity vs. log molecular weight changes from 1.0 to 3.4; thechange being associated with intermolecular entanglements. In general,the entanglement length has been defined as that length of polymerresulting from about 100 mer units. For purposes of this specification,entanglement length refers to a degree of polymerization that includes anumber of mer units on the order of magnitude of about 100 to about 250.Additional experimental techniques for determining the entanglementlength of a polymer are summarized by W. W. Graessley in ADV. POLYM.SCI., Vol. 16, 1974, and are known by those skilled in the art.

The functionalities or functional groups within a functionality clusterinclude those groups or substituents that react or interact with rubberor rubber fillers or otherwise have a desirable impact on filled rubbercompositions or vulcanizates. These groups or substituents may bereferred to as reactive functionalities. Preferably, the functionalgroups within the functionality cluster chemically bind the polymer to afiller particle. Useful substituents include trialkyltin substituentsand cyclic amine groups. Exemplary trialkyltin substituents aredisclosed in U.S. Pat. No. 5,268,439, which is incorporated herein byreference. Exemplary cyclic amino substituents are disclosed in U.S.Pat. Nos. 6,080,835; 5,786,441; 6,025,450; and 6,046,288, which areincorporated herein by reference.

The rubber fillers within the filled rubber compositions that arebelieved to react or interact with the functional groups preferablyinclude carbon black, starch, silica, alumina, aluminum hydroxide, clay,and magnesium hydroxide.

The end of the polymer chain that is opposite to the functionalitycluster (i.e., y) is not functionalized, or it may contain a weakfunctional group or a functional group that is selectively functional.Weak functional groups include those groups that interact with fillervia through-space interaction (e.g., H-bonding, van der Waalsinteraction, etc.) as well as those groups that interact with or attractto each other and thereby form a domain within the rubber matrix of thepolymer. Selective functional groups include those groups whose affinitytoward filler particles or rubber can be activated after processing;e.g. during cure. Examples of selective functional groups include thosedescribed in co-pending U.S. Ser. No. 10/020,666 now U.S. Pat. No.6,579,949.

The branch point Z can include a multi-valent atom (e.g., carbon,silicon, phosphorous) or a multi-valent chemical moiety such as ahydrocarbon group. For example, Z can be a short chain hydrocarbon groupas shown in FIG. 1.

The multi-functional polymers of this invention can be prepared by anumber of methods.

In a first embodiment, the multi-functional polymers are prepared bypolymerizing anionically-polymerizable monomers with a multi-functionalmacroinitiator.

Structurally, the multi-functional macroinitiator is an organometallicmacromolecule that includes a functionality cluster, which is definedabove.

The multi-functional macroinitiators are preferably prepared by reacting(i) an organic metallic reagent that is capable of adding to aconjugated diene or an activated olefin with (ii) a molar deficiency ofa macroinitiator linking agent. Preferably, the organometallic reagentis a short-chain living polymer.

The short-chain living polymers include anionically-polymerized polymersthat include at least one living end, i.e., carbanion and a countercation that preferably includes a lithium or magnesium cation. Theshort-chain living polymer preferably derives from the polymerization ofconjugated diene monomer alone or in combination with vinyl aromaticmonomers.

Useful conjugated diene monomers include 1,3-butadiene, isoprene,dimethyl butadiene, and 2-ethyl butadiene. Useful vinyl aromaticmonomers include styrene and ring alkyl substituted styrene.

The length of the short chain living polymer should correspond with theminimum and maximum lengths of the substituent R of the multi-functionalpolymer defined above. For example, the length of the short-chain livingpolymer should generally be longer than 0.05 of the entanglement lengthand generally shorter than 1.5 entanglement length. Accordingly, wherethe short-chain living polymer derives from 1,3-butadiene, the numberaverage molecular weight of the short-chain living polymer is preferablyfrom about 100 g/mol to about 10,000 g/mol, more preferably from about200 g/mol to about 5,000 g/mol, still more preferably 500 to about4,000, and even more preferably 1,000 to about 3,000, as determined byusing gel permeation chromatography (GPC) calibrated with polystyrenestandards and adjusted for the Mark-Houwink constants for the polymer inquestion.

The short-chain living polymer includes a reactive functionality, whichis described above. The reactive functionality preferably results froman initiator that is employed in synthesizing the short-chain livingpolymer. Useful initiators that will impart a functionality to theshort-chain living polymer include trialkyltin lithium compounds, cyclicamino lithium compounds, and cyclic aminoalkyllithium compounds.Examples of tin-lithium compounds include tributyltin lithium, which isdisclosed in U.S. Pat. No. 5,268,439, which is incorporated herein byreference. Examples of cyclic amino lithium compounds includes lithiohexamethyleneimine, which is disclosed in U.S. Pat. Nos. 6,080,835;5,786,441; 6,025,450; and 6,046,288, which are incorporated herein byreference.

The macroinitiator linking agent is a multi-functional compound thatincludes at least one anionically-polymerizable double bond and at leastone group or substituent that is susceptible to nucleophilic attack. Thepreferred macroinitiator linking agent can be defined by the formulaC═C—R¹—C*—Lwhere L is a leaving group, C* is a carbon atom susceptible tonucleophilic attack, and R¹ is an organic group that will impact thedouble bond in a manner that will allow the double bond to beanionically polymerized, i.e., it activates the double bond. A leavinggroup (e.g., L) is an atom or chemical species that is displaced from anelectrophile by a nucleophile in a nucleophilic substitution reaction.Preferably the leaving group (L) will react or associate with the livingpolymer's counter cation (e.g. Li⁺) and form a stable or neutralcompound.

In one preferred embodiment, the macroinitiator linking agent can bedefined by the formula

where R¹, R², and R³ are hydrogen or organic groups and L is a halogenatom, a sulfonate, or a phenoxide. Preferably R¹, R², and R³ arehydrogen hydrocarbyl groups, and more preferably alkyl groups havingfrom about 1 to about 6 carbon atoms. The halogen atom is preferablybromine or chlorine. The preferred sulfonates are methyl sulfonate ortoluene sulfonate.

Exemplary macroinitiator linking agents include vinylbenzyl chloride,propenyl benzyl chloride, vinyl benzyl bromide, and propenyl dimethylbenzyl chloride.

As noted above, the macroinitiators are formed by reacting theshort-chain living polymer with a molar deficiency of the macroinitiatorlinking agent. This molar deficiency will preferably include from about0.55 to about 0.99 moles of macroinitiator linking agent per mole ofshort-chain living polymer, more preferably from about 0.67 to about0.95 moles of macroinitiator linking agent per mole of short-chainliving polymer, and even more preferably from about 0.75 to about 0.93moles of macroinitiator linking agent per mole of short-chain livingpolymer.

Without wishing to be bound by any particular theory, the formation ofthe multi-functional macroinitiator can be better understood withreference to FIG. 1. Shown across the top of the proposed mechanism arethree moles of a short-chain living polymer, which are represented byBu₃Sn˜Li. The introduction of two moles of vinylbenzyl chloride (VBC)initially reacts with two of the three moles of the short-chain livingpolymer at the nucleophilic carbon site (e.g., CH₂Cl). The unreactedexcess of the short-chain living polymer (i.e., one mole) can then reactwith the VB-Bd-SnBu₃ (i.e., reaction product of the vinylbenzyl chlorideand the short-chain living polymer) to form a living species. Thisliving species can then react with the remaining one mole of theVB-Bd-SnBu₃ to form the multi-functional macroinitiator.

Monomer that may be polymerized with the multi-functional macroinitiatorinclude those monomers that are anionically polymerizable. Thesemonomers include conjugated diene monomers such as those described abovewith reference to the synthesis of the short-chain living polymer. Theseconjugated diene monomers may be copolymerized with vinyl aromaticmonomer such as styrene.

The reaction conditions that are required to conduct the anionicpolymerization with the multi-functional macroinitiator are generallyknown in the art. For example, it is common to conduct thesepolymerizations at about 30-80° C. temperature and about 205-555 kPa ofpressure.

Preferably, these polymerizations are conducted by using an organicsolvent as the polymerization medium. Useful organic solvents includealiphatic, cycloaliphatic, and aromatic hydrocarbons. Examples includen-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane,isopentane, isohexane, isoheptane, isooctane, 2,2-dimethyl butane,petroleum ether, kerosene, petroleum spirits, and isomers thereof. Somerepresentative examples of suitable cycloaliphatic solvents includecyclopentane, cyclohexane, methylcyclopentane, methyl cyclohexane, andthe like. Some representative examples of suitable aromatic solventsinclude benzene, toluene, xylene, ethyl benzene, diethyl benzene,mesitylene, and mixtures of aliphatic, cycloaliphatic and aromaticcompounds. Commercial mixtures of the above hydrocarbons, such ashexanes, may also be used. For environmental reasons, aliphatic andcycloaliphatic solvents are highly preferred.

In a second embodiment, the multi-functional polymers are prepared byterminating a living polymer with a multi-functional macroterminator.

Structurally, the multi-functional macroterminator includes a leavinggroup that is attached to a functionality cluster, which is definedabove. In one embodiment, the multi-functional macroterminator can bedefined by the formula

where Z is a branch point as defined above, Q is a functional group asdefined above, R² is an covalent bond or organic group as defined above,L is a leaving group as defined above, R³ is a multi-valent organicgroup as defined above, m is an integer that is equal to the valency ofZ, and b is an integer from 2 to m−1.

In one preferred embodiment, Z is a silicon atom, and multi-functionalmacroterminator can be defined by the formula

where Q is a functional group, R² is an a covalent bond or organicgroup, a is an integer of 2 to 3, R² is a multi-valent or an organicgroup, and A is a leaving group.

The multi-functional macroterminator may be prepared by reacting ashort-chain functionalized living polymer with a macroterminator linkingagent.

The short-chain functionalized living polymer employed in thepreparation of the macroterminator includes polymers that are similar tothe short-chain living polymers employed in the preparation of themacroinitiator, which include a filler-interactive functionality.

The macroterminator linking agent is a multi-functional reagent thatpreferably includes at least three reactive leaving groups. In oneembodiment, the macroterminator linking agent can be defined by theformula L_(b)Z(R⁴A)_((m-b)), where Z is a branch point, R⁴ is a covalentbond or a multi-valent organic group, L is a leaving group, A is aleaving group that is less reactive than L, m is equal to the valency ofZ, and b is an integer from 2 to m−1. In a preferred embodiment, Z issilicon, and therefore the macroterminator linking agents can be definedby the formula L_(a)Si(R⁴A)_((4-a)), where Si is a silicon atom, R⁴ isan organic group, L is a leaving group, A is a leaving group that isless reactive than L, and a is 2 or more. The term less reactive than Lrefers to the fact that a nucleophile will, on a statistical basis,replace L prior to replacing A.

Exemplary macroterminator linking agents include trichlorosiliconmethylene chloride, tribromosilicon methylene chloride, trichlorosiliconmethylene bromide, and 3-glycidoxypropyltrimethoxysilane (GPMOS).

In a preferred embodiment, the molar ratio of short-chain living polymer(i.e., lithium atom) to macroterminator linking agent is preferablydetermined based upon the number of equivalents of L withinL_(b)Z(R⁴A)_((m-b)). In other words, one equivalent of lithium (i.e.,living polymer) is reacted with one equivalent of L (i.e., the integerrepresented by b). The resultant multi-functional macroterminator can berepresented by the formula

where Q, R⁴, R′, A, and a are defined above.

Anionically-polymerized living polymers are formed by reacting anionicinitiators with unsaturated monomers to propagate a polymeric structure.Throughout formation and propagation of the polymer, the polymericstructure is anionic and “living.” A living polymer, therefore, is apolymeric segment having a living or reactive end. For example, when alithium (Li) containing initiator is employed to initiate the formationof a polymer, the reaction produces a reactive polymer having a Li atomat its living end. This living end remains after complete polymerizationso that a new batch of monomer subsequently added to the reaction canadd to the existing chains and increase the degree of polymerization.For further information respecting anionic polymerizations, one canrefer to PRINCIPLES OF POLYMERIZATION, 3^(RD) EDITION, by George Odian,John Wiley & Sons, Inc. (1991), Chapter 5, entitled Ionic ChainPolymerization, or Panek et al., J. AM. CHEM. SOC., 94, 8768 (1972).

Monomers that can be employed in preparing a living polymer include anymonomer capable of being polymerized according to anionic polymerizationtechniques. These monomers include those that lead to the formation ofelastomeric homopolymers or copolymers. Suitable monomers include,without limitation, conjugated C₄-C₁₂ dienes, C₈-C₁₈ monovinyl aromaticmonomers, and C₆-C₂₀ trienes. Examples of conjugated diene monomersinclude, without limitation, 1,3-butadiene, isoprene, 1,3-pentadiene,2,3-dimethyl-1,3-butadiene, and 1,3-hexadiene. A non-limiting example oftrienes includes myrcene. Aromatic vinyl monomers include, withoutlimitation styrene, α-methyl styrene, p-methylstyrene, andvinylnaphthalene. When preparing elastomeric copolymers, such as thosecontaining conjugated diene monomers and aromatic vinyl monomers, theconjugated diene monomers and aromatic vinyl monomers are normally usedat a ratio of 95:5 to 50:50, and preferably 95:5 to 65:35.

Any anionic initiator can be employed to initiate the formation andpropagation of the living polymers. Exemplary initiators include, butare not limited to, alkyl lithium initiators such as n-butyl lithium,arenyllithium initiators, arenylsodium initiators, N-lithiumdihydro-carbon amides, aminoalkyllithiums, and alkyl tin lithiums. Otheruseful initiators include N-lithiohexamethyleneimide,N-lithiopyrrolidinide, and N-lithiododecamethyleneimide as well asorganolithium compounds such as substituted aldimines, substitutedketimines, and substituted secondary amines. Exemplary initiators arealso described in the following U.S. Pat. Nos. 5,332,810, 5,329,005,5,578,542, 5,393,721, 5,698,646, 5,491,230, 5,521,309, 5,496,940,5,574,109, and 5,786,441, which are incorporated herein by reference.

The amount of initiator employed in conducting anionic polymerizationscan vary widely based upon the desired polymer characteristics. In oneembodiment, it is preferred to employ from about 0.1 to about 100, andmore preferably from about 0.33 to about 10 mmol of lithium per 100 g ofmonomer.

In order to promote randomization in copolymerization and to controlvinyl content, a polar coordinator may be added to the polymerizationingredients. Amounts range between 0 and 90 or more equivalents perequivalent of lithium. The amount depends on the amount of vinyldesired, the level of styrene employed and the temperature of thepolymerization, as well as the nature of the specific polar coordinator(modifier) employed. Suitable polymerization modifiers include, forexample, ethers or amines to provide the desired microstructure andrandomization of the comonomer units.

Examples include dialkyl ethers of mono and oligo alkylene glycols;“crown” ethers; tertiary amines such as tetramethylethylene diamine(TMEDA); linear THF oligomers; and the like. Specific examples ofcompounds useful as polar coordinators include tetrahydrofuran (THF),linear and cyclic oligomeric oxolanyl alkanes such as2,2-bis(2′-tetrahydrofuryl)propane, di-piperidyl ethane, dipiperidylmethane, hexamethylphosphoramide, N—N′-dimethylpiperazine,diazabicyclooctane, dimethyl ether, diethyl ether, tributylamine and thelike. The linear and cyclic oligomeric oxolanyl alkane modifiers aredescribed in U.S. Pat. No. 4,429,091, owned by the Assignee of record,the subject matter of which relating to such modifiers is incorporatedherein by reference. Compounds useful as polar coordinators includethose having an oxygen or nitrogen hetero-atom and a non-bonded pair ofelectrons.

Anionic polymerizations are typically conducted in a polar or non-polarsolvent such as tetrahydrofuran (THF) or a nonpolar hydrocarbon such asthe various cyclic and acyclic hexanes, heptanes, octanes, pentanes,their alkylated derivatives, and mixtures thereof.

In another embodiment, the macroterminating linking agent can be definedby the formula Z(R⁵L)_(m), where Z is a branch point as defined above,R⁵ is a covalent bond or a multi-valent organic group, L is a leavinggroup, and m is equal to the valency of Z. In a preferred example, Z isa silicon atom, and therefore the macroterminator linking agent can bedefined by the formula Si(R⁵L)₄. Where R⁵ is a covalent bond and L is achlorine atom, the macroterminating linking agent is silicontetrachloride.

In another embodiment, the multi-functional polymers can be prepared byreacting a polymer containing a leaving group cluster with short-chainfunctionalized living polymers. The polymer containing a leaving groupcluster can be defined by the formula

where L is a leaving group, R⁶ is a covalent bond or a multi-valentorganic group, Z is a branch point, P² is long-chain polymer, Y is aproton, a weak functional group, or a selective functional group, and mis an integer that is equal to the valency of Z, all of which aredefined above. The short-chain functionalized living polymer that isreacted with this polymer containing a leaving group cluster includespolymers that are similar to the short-chain living polymers employed inthe preparation of the macroinitiator, which preferably include afiller-interactive functionality. The reaction preferably takes place byreacting m equivalents of short-chain functionalized living polymer withthe polymer containing the leaving group cluster.

The polymer containing the leaving group cluster can be prepared byusing several techniques. In one embodiment, a long-chain living polymeris terminated with a terminating agent having the formula Z(R⁵L)_(m)where Z is a branch point, R⁷ is a covalent bond or a multi-valentorganic group, L is a leaving group, and m is an integer equal to thevalency of Z.

Where this compound is silicon tetrachloride, the reaction is conductedby reacting about 1 mole of the long-chain living polymer with about 1mole of silicon tetrachloride at room temperature. Although various sideproducts may result, the resulting polymer containing a leaving groupcluster will include a long-chain polymer having a silicon trichloridefunctionality at its terminal end. An excess of silicon tetrachloridecan be used to improve yield of the desired product. This polymer canthen be reacted with short chain living polymer to produce themulti-functional polymers of this invention via a nucleaphilicsubstitution reaction at the three chlorine atoms. Accordingly, it ispreferred to react about 3 moles of the short-chain functionalizedliving polymer with one mole of the polymer containing the leaving groupcluster (i.e., 1 mole of short-chain functionalized living polymer perequivalent of chlorine).

In another embodiment, the terminating agent that is reacted with thelong-chain living polymer to produce the polymer containing a leavinggroup cluster can be defined by the formula L_(b)Z(R⁸L)_(m-b) where L isa leaving group, Z is a branch point, R⁸ is a covalent bond ormulti-valent organic group, m is equal to the valency of Z, and b is aninteger from 2 to m−1.

Where this terminating agent is 3-glycidoxypropyltrimethoxysilane(GPMOS), it is believed that the living long-chain polymer will reactwith the GPMOS at the epoxide site (i.e., the oxygen acting as theleaving group and the living polymer covalently bonding with the highlyelectrophilic carbon atom of the epoxide ring). Other useful products,however, may result through reaction of the living polymer with thesilicon atom by displacing a methoxy group from the silicon atom. Theleaving group cluster will be formed by the three methoxy groups ofGPMOS, or two of the methoxy groups and the oxygen of the epoxide group.These methoxy groups will act as leaving groups when reacted withshort-chain functionalized living polymers to form the multi-functionalpolymers of this invention.

The reaction between the long-chain living polymer and GPMOS preferablyoccurs at about 50° C. at a molar ratio of about 1 GPMOS to about 1living polymer. The reaction between the resulting polymer containing aleaving group cluster and the short-chain living polymer is preferablyconducted at a molar ratio of about 1 polymer containing the leavinggroup cluster to about 3 short-chain functionalized living polymers,although a molar excess of the GPMOS can be used to improve yield of thedesired product.

In another embodiment, the multi-functional polymers are prepared bypolymerizing hetero-blocks at the head or tail of a rubbery polymer. Thehetero-block is prepared by polymerizing short chains of functionalmacromonomers. For purposes of this specification, the head of thepolymer will refer to that point of the polymer main chain where theinitiator adds to the first monomer. The tail will therefore refer tothat point of a polymer main chain where the last monomer is added tothe chain, i.e., the polymer is terminated.

Where the functional macromonomers are polymerized into a hetero-blockat the head of a polymer chain, the polymerization of the functionalmacromonomers can be initiated with any anionic polymerizationinitiator. These initiators can include conventional organometalliccompounds such as butyl lithium, or functionalized initiators such astributyltin lithium or lithium hexamethyleneimine. The functionalmacromonomer is charged first, allowing the polymerization initiator toform a short functional block (i.e., hetero block). The other monomersto be polymerized, e.g., 1,3-butadiene and styrene, are then charged tothe same system, and the polymerization is continued in a conventionalmanner. The resulting living polymer can then be terminated with aproton or a functionalized terminator that will impart a weak orselective functional group to the tail of the polymer.

Where the functional macromonomers are added to the tail of a rubberypolymer, the polymerization of monomer (e.g., 1,3-butadiene and styrene)is initiated with an anionic polymerization initiator. This initiatorwill preferably not impart a functional group to the head of thepolymer, e.g., butyl lithium, or only provide a weak or selectivefunctional group to the head. With these initiators, a living rubberypolymer is prepared by employing conventional techniques. Once theliving polymer is prepared to a desired molecular weight, functionalmacromonomers are added to the same system and polymerization iscontinued to form a hetero block at the polymer tail. The number ofpolymeric units that derive from the functional macromonomers can becontrolled by regulating the amount of functional macromonomer added tothe system or by adding a polymerization terminator, e.g., alcohol. Thepolymerization terminator can also be a reagent capable of imparting afunctional group to the tail of the polymer, e.g., tributyltin chloride.

The functional macromonomer is a macromolecule that includes a doublebond capable of being anionically polymerized, e.g., a conjugated doublebond, a functional group, and an organic group between the double bondand the functional group where the distance between the double bond andthe functional group is less than one entanglement length.

An exemplary multifunctional macromonomer can be prepared by reacting ashort chain living polymer that contains a functional group at its headwith a compound that is similar to the macroinitiator linking agentdefined above, e.g., vinylbenzyl chloride. The reaction product of theshort chain living polymer and vinylbenzyl chloride will yield afunctional macromonomer that can be defined by the following structure:

where Q is a functional group and R is a organic group. Preferably, R isa short-chain polymer that has a length that is less than oneentanglement length.

Other examples include derivatives of conjugated diene monomers. Oneexample of a derivative of a conjugated diene monomer is

where Q is a functional group.

After formation of the multi-functional polymer, a processing aid andother optional additives such as oil can be added to the polymer cement.The multi-functional polymer and other optional ingredients are thenisolated from the solvent and preferably dried. Conventional proceduresfor desolventization and drying may be employed. In one embodiment, themulti-functional polymer may be isolated from the solvent by steamdistillation of the solvent followed by filtration. Residual solvent maybe removed by using conventional drying techniques such as a drum dryer.Alternatively, the cement may be directly drum dried.

The multi-functional polymers of this invention are particularly usefulin preparing tire components. These tire components can be prepared byusing the multi-functional polymers of this invention alone or togetherwith other rubbery polymers. The preparation of vulcanizablecompositions and the construction and curing of the tire is not affectedby the practice of this invention.

In preparing the vulcanizable compositions of matter, at least onefiller may be combined and mixed or compounded with a rubber component,which includes the multi-functional polymer of this invention as well asother optional rubber polymers. Other rubbery elastomers that may beused include natural and synthetic elastomers. The synthetic elastomerstypically derive from the polymerization of conjugated diene monomers.These conjugated diene monomers may be copolymerized with other monomerssuch as vinyl aromatic monomers. Other rubbery elastomers may derivefrom the polymerization of ethylene together with one or more α-olefinsand optionally one or more diene monomers.

Useful rubbery elastomers include natural rubber, syntheticpolyisoprene, polybutadiene, polyisobutylene-co-isoprene, neoprene,poly(ethylene-co-propylene), poly(styrene-co-butadiene),poly(styrene-co-isoprene), and poly(styrene-co-isoprene-co-butadiene),poly(isoprene-co-butadiene), poly(ethylene-co-propylene-co-diene),polysulfide rubber, acrylic rubber, urethane rubber, silicone rubber,epichlorohydrin rubber, and mixtures thereof. These elastomers can havea myriad of macromolecular structures including linear, branched andstar shaped. Other ingredients that are typically employed in rubbercompounding may also be added.

The rubber compositions may include fillers such as inorganic andorganic fillers. The organic fillers include carbon black and starch.The inorganic fillers may include silica, aluminum hydroxide, magnesiumhydroxide, clays (hydrated aluminum silicates), and mixtures thereof.

A multitude of rubber curing agents may be employed. For example, sulfuror peroxide-based curing systems may be employed. Also, see Kirk-Othmer,ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY, 3^(rd) Edition, Wiley Interscience,N.Y. 1982, Vol. 20, pp. 365-468, particularly VULCANIZATION AGENTS ANDAUXILIARY MATERIALS pp. 390-402, or Vulcanization by A. Y. Coran,ENCYCLOPEDIA OF POLYMER SCIENCE AND ENGINEERING, 2^(nd) Edition, JohnWiley & Sons, Inc., 1989, which are incorporated herein by reference.Vulcanizing agents may be used alone or in combination.

Other ingredients that may be employed include accelerators, oils,waxes, scorch inhibiting agents, processing aids, zinc oxide, tackifyingresins, reinforcing resins, fatty acids such as stearic acid, peptizers,and one or more additional rubbers.

Preferably, the vulcanizable rubber composition is prepared by formingan initial masterbatch that includes the rubber component and filler.This initial masterbatch is mixed at a starting temperature of fromabout 25° C. to about 100° C. with a discharge temperature of about 135°C. to about 180° C. To prevent premature vulcanization (also known asscorch), this initial masterbatch generally excludes any vulcanizingagents. Once the initial masterbatch is processed, the vulcanizingagents are introduced and blended into the initial masterbatch at lowtemperatures in a final mix stage, which does not initiate thevulcanization process. Optionally, additional mixing stages, sometimescalled remills, can be employed between the masterbatch mix stage andthe final mix stage. Rubber compounding techniques and the additivesemployed therein are generally known as disclosed in the in TheCompounding and Vulcanization of Rubber, by Stevens in RUBBER TECHNOLOGYSECOND EDITION (1973 Van Nostrand Reinhold Company). The mixingconditions and procedures applicable to silica-filled tire formulationsare also well known as described in U.S. Pat. Nos. 5,227,425; 5,719,207;5,717,022, as well as EP 0890606, all of which are incorporated hereinby reference.

Where the vulcanizable rubber compositions are employed in themanufacture of tires, these compositions can be processed into tirecomponents according to ordinary tire manufacturing techniques includingstandard rubber shaping, molding and curing techniques. Typically,vulcanization is effected by heating the vulcanizable composition in amold; e.g., it is heated to about 170° C. Cured or crosslinked rubbercompositions may be referred to as vulcanizates, which generally containthree-dimensional polymeric networks that are thermoset. The otheringredients, such as processing aides and fillers, are generally evenlydispersed throughout the vulcanized network. Tire components of thisinvention preferably include tire treads. The rubber compositions,however, can also be used to form other elastomeric tire components suchas subtreads, sidewalls, body ply skims, bead fillers and the like.Pneumatic tires can be made as discussed in U.S. Pat. Nos. 5,866,171;5,876,527; 5,931,211; and 5,971,046, which are incorporated herein byreference.

In order to demonstrate the practice of the present invention, thefollowing examples have been prepared and tested. The examples shouldnot, however, be viewed as limiting the scope of the invention. Theclaims will serve to define the invention.

EXAMPLES Example I Preparation of Macroinitiator

To each of four oven-dried N₂ purged 800 ml bottles fitted with crimpedcap and a rubber liners, were charged a mixture of hexanes (48 g) andbutadiene blend (21.4% in hexanes, 102 g) to a concentration ofapproximately 14% total solids. A polar modifier (0.11 mmol) was addedfollowed by tributyl tin lithium (Bu₃SnLi) (10.9 mmol). After one hourof agitation in a 50° C. heating bath, the solution was treated with4-vinylbenzyl chloride (7.28 mmol). This solution was agitated by handat room temperature for 2-5 minutes and used within 10 minutes.

Example II Preparation of Polymer from Macroinitiator (Samples 1-3)

A 19 L reactor was charged with hexanes (2.3 kg), styrene blend (34% inhexanes, 1.6 kg), butadiene blend (21.9% in hexanes, 7.4 kg), polarmodifier (1.44 mmol) and all 4 bottles of macroinitiator from Example I(14.4 mmol of Li). The reactor was heated in batch mode at 50° C.,exotherming from 70°-75° C. After two hour, the polymer was dropped intoisopropyl alcohol and antioxidant, isolated and drum-dried. This polymeris represented as Sample 1 in Table I. Samples 2 and 3, which are alsoset forth in Table I, were prepared by using the same procedures as setforth for preparing Sample 1.

The characteristics of the multi-functional polymers that were preparedare set forth in Table I.

Example III Preparation of Macroinitiator

To an oven-dried N₂ purged 800 ml bottle fitted with crimped cap and arubber liner, was charged a mixture of hexanes (175 g) and butadieneblend (21.8% in hexanes, 148 g) to a concentration of approximately 10%total solids. A polar modifier (0.16 mmol) was added followed byisoprene extended hexamethyleneimine (HMI) propyllithium initiator (16.1mmol). After one hour of agitation in a 50° C. heating bath, thesolution was treated with 4-vinylbenzyl chloride (11.9 mmol). Thissolution was agitated by hand at room temperature for 2-5 minutes andused within 10 minutes.

Example IV Preparation of Polymer from Macroinitiator (Sample 4)

An 8 L reactor was charged with hexanes (2.3 kg), styrene blend (34% inhexanes, 1.2 kg), butadiene blend (21.8% in hexanes, 5.6 kg), polarmodifier (0.4 mmol) and all of the macroinitiator in Example IV (3.9mmol of Li). The reactor was heated in batch mode at 50° C., exothermingfrom 55°-60° C. After two hours, the polymer was dropped into isopropylalcohol and antioxidant, isolated and drum-dried.

The characteristics of the multi-functional polymers that were preparedare set forth in Table I.

Example V Preparation of Unfunctionalized Macroinitiator

In a similar fashion to Example I, three macroinitiators were preparedexcept that n-butyl lithium (BuLi) was employed to initiatepolymerization of the short polymer chains in lieu of tributyl tinlithium (Bu₃SnLi). As a result, the resulting architecture of themacroinitiators were the same as those prepared in Example I, exceptthat the various branches were not functionalized.

Example VI Preparation of Polymer from Unfunctionalized Macroinitiator(Samples 5-7)

In a similar fashion to Example II, three polymers were prepared usingthe unfunctionalized initiators prepared in Example V. The resultingarchitecture of the polymer was the same as those prepared in Example IIexcept that the head of the polymer, which was branched, was notfunctionalized. The three polymers, which are identified as Samples 5-7,where characterized as set forth in Table I.

TABLE I Number of Sample Functional Functional Mooney Styrene T_(g) SnNo. Group Groups M_(n) M_(w) M_(n)/M_(w) ML₁₊₄ @ 100° C. (% wt) (° C.)(ppm) 1 alkyl-tin 2–3 153,000 221,000 1.45 50.5 23.5 −47.9 1,419 2alkyl-tin 2–3 187,000 246,000 1.31 78.7 24.0 −42.6 1,384 3 alkyl-tin 2–3132,000 203,000 1.54 51.5 22.3 −44.7 1,099 4 HMI 2–3 134,000 226,0001.68 63.8 25 −51 — 5 None — 159,760 194,584 1.22 46 20.3 −49 — 6 None —176,384 345,756 1.39 82.5 20.3 47.2 — 7 None — 210,048 309,706 1.47103.5 22.1 44.2 —

Example VII Preparation of Vulcanizate (Compounds 1-X, 1-1 Through 1-7)

The rubbery polymers prepared above were mixed into a tire compound andanalyzed for various properties before and after curing. The tirecompound recipe that was employed is set forth in Table II.

TABLE II Ingredient Parts by Weight Rubbery Polymer 70 Natural Rubber 30Carbon Black 41 Wax 1.0 Antidegradant 0.95 Zinc Oxide 2.5 Stearic Acid2.0 Naphthenic Oil 5.25 Aromatic Oil 5.25 Sulfur 1.3 Accelerator 1.7Accelerator 0.2

The characteristics of the compound and vulcanizates are set forth inTable III.

The rubber employed in Compound 1-X was functionalizedpoly(styrene-co-butadiene) that had a styrene content of about 35%, a Tgof about −40° C., and a Mooney Viscosity (ML₁₊₄@100° C.) of about 70.This poly(styrene-co-butadiene) control was initiated with tributyl tinlithium and terminated with equal parts of tin tetrachloride andtributyl tin chloride.

After mixing, the compounds were analyzed for carbon black dispersionand Mooney Viscosity (ML₁₊₄@130° C.). Carbon black dispersion(Surfanalyzer Dispersion Index) was measured according to ASTM D 2663,Test Method C (1995), except that the same calibration values, A and B,were used for all test samples with periodic review of the calculateddispersion ratings relative to dispersion estimates from light opticalmicroscopy.

TABLE III Compound 1-X 1-1 1-2 1-3 1-4 1-5 1-6 1-7Poly(styrene-co-butadiene) Control Sample 1 Sample 2 Sample 3 Sample 49Sample 5 Sample 6 Sample 7 Surfanalyzer (average of 2) 68.2 77.8 79.785.9 66.3 95.8 88.2 81.2 Compound Mooney ML₁₊₄ @ 130° C. 56.7 41.2 41.735.6 52.6 33.1 42.9 47.4 Ring Tensile @ 23° C. 300% Modulus (MPa) 9.368.4 8.93 8.54 9.34 7.89 8.49 8.18 Tensile @ Break (MPa) 18.24 19.4619.68 19.97 21.06 18.31 20.99 18.06 Elongation @ Break (%) 442 490 481493 490 509 530 488 Ring Tensile @ 100° C. 300% Modulus (MPa) 7.57 6.616.69 6.65 6.27 6.71 6.61 Tensile @ Break (MPa) 8.20 8.34 7.69 8.78 7.728.44 10.02 9.53 Elongation @ Break (%) 315 346 327 353 490 364 391 378Ring Tear @ 23° C. (kN/m) 60.2 68.2 67.2 69.0 63.2 68.6 72.4 70.2 RingTear @ 117° C. (kN/m) 22.4 29.4 30.2 27.2 27.2 28.4 43.2 29.6 Dynastat(1 Hz at 2% strain) M′ @ 50° C. (MPa) 5.272 5.205 4.851 4.748 6.171 5.395.37 5.45 tan δ @ 50° C. 0.092 0.093 0.102 0.095 0.100 0.138 0.133 0.119Strain Sweep (1 Hz) @ 23° C. tan δ @ 5% strain 0.110 0.116 0.120 0.1150.119 0.167 0.173 0.144 ΔG′ [0.25-14%] (MPa) 0.564 0.543 0.654 0.5010.565 1.59 1.35 1.36 Torsion Rectangular tan δ @ 50° C. 0.087 0.0990.096 0.092 0.095 0.158 0.149 0.117

The data of Table III was employed to graph the tan δ of the varioussamples as a function of percent bound rubber at room temperature. Thisgraph is represented in FIG. 2. This graph also includes anothercontrol, which is represented as compound 1-Y. This compound wasprepared by employing a poly(styrene-co-butadiene) that was prepared andterminated in a similar fashion to the polymer used in Compound 1-Xexcept that the polymer was initiated with n-butyllithium (i.e., no headfunctionalization; only one functional group at the tail).

Test specimens of each rubber formulation were prepared by cutting outthe required mass from an uncured sheet (about 2.5 mm to 3.81 mm thick).Test specimens were cured within closed cavity molds under pressure for13 minutes at 165° C. Modulus at 300%, elongation at break, and tensilestrength were measured according to ASTM D 412 (1998) Method B, wheresamples were died from a cured sheet about 1.8 mm thick. Rubbercylinders measuring about 9.5 mm in diameter and 16 mm high wereanalyzed by using a Dynastat viscoelastic analyzer and an RDA(Reometrics Dynamic Analyzer). Dynastat M′, RDA G′, and Dynastat tan δare reported in Table III.

Example VIII Preparation of Macroterminator

To each of 3 oven-dried N₂ purged 800 mL bottles fitted with crimped capand rubber liners, were charged a mixture of hexanes (36 g) andbutadiene blend (22.5%, 14.4 g) to a concentration of 16% total solids.A polar modifier (0.26 mmol) was added followed by tributyl tin lithium(Bu₃SnLi) (0.8 mmol). After one hour of agitation in a 50° C. heatingbath, the bottles were agitated in a room temperature heating bath for20 minutes. A solution of SiCl₄ was added (0.24 mmol) and the bottlesagitated at room temperature for 30 minutes. These solutions were thenused as macroterminators for higher molecular weight polymers.

Example IX Termination of Living Polymer with Macroterminator (Samples 8& 9)

A 19 L reactor was charged with hexanes (14.5 lbs.), styrene blend (34%in hexanes, 1.7 lbs.), butadiene blend (22.5% in hexanes, 8.6 lbs.),polar modifier (2.0 mmol) and BuLi (8.1 mmol). The reactor was heated toan exotherm temperature of 70-75° C. After 1.5 hours of reaction time,the polymer-lithium cement (Li:Si—Cl ratio=1:1) was dropped into bottlescontaining the macroterminator solutions prepared in Example VIII. Thesebottles were agitated at 50° C. for one hour, isolated and drum-dried.

Example X Preparation of Polymer Containing Leaving Group Cluster

A 19 L reactor was charged with hexanes (11.4 lbs.), styrene blend (34%in hexanes, 2.7 lbs.), butadiene blend (22.5% in hexanes, 15.7 lbs.),polar modifier (6.1 mmol) and BuLi (18.6 mmol). The reactor was heatedto an exotherm temperature of 65-70° C. After 1.5 hours of reactiontime, the polymer-lithium cement was dropped into oven-dried N₂ purged800 mL bottles fitted with crimped cap and rubber liners. Each bottlewas treated with 1 equivalent per lithium of3-glycidoxypropyltrimethooxysilane (GPMOS). The terminated polymer wasthen reacted further in Example XI.

Example XI Reaction of Leaving Group Cluster with Short-Chain Polymer(Sample 10)

A 19 L reactor was charged with hexanes (15.4 lbs.) and butadiene blend(21% in hexanes, 15.4 lbs.), polar modifier (25 mmol) and tributyl tinlithium (76 mmol). The reactor was heated to an exotherm temperature of55-60° C. After 1.5 hours of reaction time, the polymer-lithium cement(3 equivalents per Li) was dropped into bottles containing theterminated polymer from Example X (1 equivalent per lithium). Thebottles were agitated at 50° C. for 1 hour, isolated and drum-dried.

Example XII Preparation of Vulcanizate (Compounds 1-Y, 1-Z, and 1-8through 1-10)

The rubbery polymers prepared above were mixed into a tire compoundusing conventional techniques and analyzed for various properties beforeand after curing. The tire compound recipe that was employed is setforth in Table IV.

TABLE IV Ingredient Parts by Weight Rubbery Polymer 100 Carbon Black 55Wax 1.0 Antidegradant 0.95 Zinc Oxide 2.5 Stearic Acid 2.0 Oil 10 Sulfur1.3 Accelerator 1.7 Accelerator 0.2

The characteristics of the compound and vulcanizates are set forth inTable V. The length of the polymer chain within the functionalitycluster of the multi-functional polymers is set forth as the arm length.

The rubber employed in Compound 1-Y was functionalizedpoly(styrene-co-butadiene) that had a styrene content of about 35%, a Tgof about −40° C., and a Mooney Viscosity (ML₁₊₄@100° C.) of about 70.This poly(styrene-co-butadiene) control was initiated with tributyl tinlithium and terminated with equal parts of tin tetrachloride andtributyl tin chloride.

The polymer used in compound 1-Z was prepared by using n-butyl lithiumas an initiator and isopropyl alcohol as a quenching agent. This polymerlikewise had a styrene content of about 20% and a butadiene content ofabout 80%.

After mixing, the compounds were analyzed for carbon black dispersionand Mooney Viscosity (ML₁₊₄@130° C.). Carbon black dispersion(Surfanalyzer Dispersion Index) was measured according to ASTM D 2663,Test Method C (1995), except that the same calibration values, A and B,were used for all test samples with periodic review of the calculateddispersion ratings relative to dispersion estimates from light opticalmicroscopy.

TABLE V Compound 1-Y 1-Z 1-8 1-9 1-10 Poly(styrene-co- Control ControlSample Sample Sample butadiene) 1 2 8 9 10 Arm Length (kg/mol) n/a n/a 123 15 Tg (° C.) −40.0 −33.2 −40.1 −41.3 −36.0 Mn (kg/mol) 178 114 73 169154 Mw/Mn 1.57 1.06 2.07 1.53 4.25 Compound Mooney 98.1 25.9 67.6 66.959.8 ML₁₊₄ @ 130° C. Ring Tensile @ 23° C. 300% Modulus (MPa) 14.0 11.214.4 13.6 13.8 Tensile @ Break (MPa) 22.5 16.0 21.0 17.0 17.7 Dynastat(1 Hz at 5% strain) tan δ @ 50° C. 0.119 0.254 0.106 0.146 0.165 StrainSweep (1 Hz) @ 50° C. tan δ @ 5% strain 0.118 0.257 0.105 0.143 0.165ΔG′ [0.25–14%] (MPa) 1.07 4.69 0.73 1.09 1.66 Bound Rubber (%) 50.4 13.847.8 42.4 30.2

Various modifications and alterations that do not depart from the scopeand spirit of this invention will become apparent to those skilled inthe art. This invention is not to be duly limited to the illustrativeembodiments set forth herein.

1. A process for preparing a multi-functional polymer comprising thesteps of: preparing a multi-functional macroinitiator by reactingshort-chain living polymer with a molar deficiency of a macroinitiatorlinking agent defined by the formulaC═C—R¹—C*—X where X is a leaving group, C* is a carbon atom susceptibleto nucleophilic attack, and R¹ is an organic group that will impact thedouble bond in a manner that will allow the double bond to beanionically polymerized, where the short-chain living polymer ischaracterized by a length that is longer than 0.05 of the entanglementlength and shorter than 1.5 of the entanglement length, where the saidshort-chain living polymer includes a functional group in addition to aliving end, and where the functional group derives from synthesizing theshort-chain living polymer with an initiator selected from the groupconsisting of trialkyltin lithium compounds, cyclic amino lithiumcompounds, and cyclic amino alkyllithium compounds; and polymerizingmonomer with the multi-functional macroinitiator.
 2. The process ofclaim 1, where the molar deficiency includes from about 0.55 to about0.95 moles of macroinitiator linking agent per mole of short-chainliving polymer.
 3. The process of claim 1, where the macroinitiatorlinking agent is vinylbenzyl chloride.
 4. The process of claim 1, wherethe monomer is conjugated diene monomer.
 5. The process of claim 4,where the monomer further includes styrene.
 6. The process of claim 1,where the short-chain living polymer is characterized by a length thatis less than 1 of the entanglement length.
 7. The process of claim 1,where the short-chain living polymer is characterized by a length thatis less than 0.7 of the entanglement length.
 8. The process of claim 1,where the short-chain living polymer is characterized by a length thatis less than 0.5 of the entanglement length.
 9. The process of claim 1,where the short-chain living polymer includes living polybutadiene. 10.The process of claim 9, where the living polybutadiene has a numbermolecular weight of from about 100 to about 10,000 g/mol as determinedby GPC.
 11. The process of claim 10, where the living polybutadiene hasa number molecular weight of from about 200 to about 5,000 g/mol asdetermined by GPC.
 12. The process of claim 11, where the livingpolybutadiene has a number molecular weight of from 500 to about 4,000g/mol as determined by GPC.
 13. The process of claim 12, where theliving polybutadiene has a number molecular weight of from 1,000 toabout 3,000 g/mol as determined by GPC.
 14. The process of claim 1,where the macroinitiator linking agent is defined by the formula

where R¹, R², and R³, are hydrogen or organic groups, and L is a halogenatom, a sulfonate, or a phenoxide.
 15. The process of claim 14, whereR¹, R², and R³ are hydrogen or hydrocarbyl groups.
 16. The process ofclaim 1, where the macroinitiator linking agent is vinylbenzyl chloride,propenyl benzyl chloride, vinyl benzyl bromide, or propenyl dimethylbenzyl chloride.
 17. The process of claim 2, where the molar deficiencyincludes from about 0.67 to about 0.95 moles of macroinitiator linkingagent per mole of short-chain living polymer.
 18. The process of claim17, where the molar deficiency includes from about 0.75 to about 0.93moles of macroinitiator linking agent per mole of short-chain livingpolymer.
 19. The process of claim 1, where said step of polymerizingmonomer with the multi-functional macroinitiator occurs within anorganic solvent.
 20. The process of claim 19, where the organic solventis an aliphatic solvent.